Summarizing the following 3 propositions – emotions are stronger...
1. if their cause is present
2. if we think of their cause is close at hand rather than distant
3. if we conceive of their cause as necessary
Proposition XII. An emotion towards a thing, which we know not to exist at the present time, and which we conceive as possible, is more intense, other conditions being equal, than an emotion towards a thing contingent.
Proposition XIII. Emotion towards a thing contingent, which we know not to exist in the present, is, other conditions being equal, fainter than an emotion towards a thing past.
Spinoza spells out some of the conditions pertaining to the strength of the emotions. If their cause is present, thought soon to happen, necessary according to the Laws of Nature, they are stronger. If their cause is only possible or does not presently exist, they are weaker. Whether we know their cause in good or bad makes no difference unless the knowledge is converted into an emotion. An emotion that is present can only be replaced by a stronger one.